Electrosurgical instruments have been used for many years in high-frequency surgery especially in order to coagulate biological tissue as well as to cut it. For coagulation a high-frequency current is passed through the tissue to be treated, so that it changes due to protein coagulation and dehydration. The tissue contracts in such a way that the vessels are closed and bleeding is staunched. After coagulation has taken effect the tissue can, for example, be separated by means of a mechanically operating cutting instrument.
Electrosurgical procedures can be carried out in a monopolar as well as a bipolar way. With monopolar technology the electrosurgical instrument has only one current supply and the tissue to be treated (or the patient) must therefore be placed at the other potential. Bipolar instruments which are constructed with two separately isolated sections are gaining more and more in significance, however. The current path between the electrode parts can thus be calculated and does not run long distances through the body of the patient. The effect of, for example, pacemakers or other equipment which are connected to the patient during an operation is thus reduced.
Bipolar coagulation instruments comprise essentially two limbs that have an articulated connection at whose proximal ends handle devices are provided for handling the limbs. At the distal ends of the limbs are electrode parts with coagulation surfaces for gripping the tissue and for passing the coagulation current through the tissue. For this the HF current supplied by a HF generator is fed via current supply devices to the electrode parts of the bipolar instrument.
Known bipolar coagulation instruments often comprise open regions on the electrode parts forming a guide gap for a cutting instrument. This means that the electrode parts are at least partially divided, so that cutting instrument can be placed on the tissue clamped between the electrode parts. The guide gap therefore facilitates access for the cutting instrument to the tissue while being held between the electrode parts of the coagulation instrument. Also, the guide gap is provided to guide the cutting instrument in order to guarantee precise cutting of the tissue. This is advantageous particularly for mechanically operated cutting instruments.
Such an instrument is, for example, known from US 2003/0229344 A1. Bipolar tongs are shown where the effector unit and in particular its electrically conductive areas comprise slits to facilitate access for a cutting instrument to the tissue clamped in the effector unit. The slits are constructed in such a way that the coagulation surfaces of the electrode parts are disrupted as little as possible. With this embodiment of the slits their preparation for reuse, that is to say cleaning, is very time-consuming as the access into the slits is made difficult.
In order to counteract this problem a very wide slit or guide gap is provided in other known instruments. Here a considerable reduction in the coagulation surfaces or insufficient guidance of mechanical cutting instruments in particular has to be accepted.
Known instruments are also provided as disposable instruments in order to save cleaning. This has considerable cost implications.